The present invention relates to a method for updating the transmissibility function of a clutch during a gear change, and in particular a gear change performed by a servo-controlled manual gear change to which the following description will make explicit reference without detriment to its general nature.
Servo-controlled manual gear changes are increasingly widespread and, from a structural point of view, are entirely similar to a conventional manual gear change except for the fact that the control pedals and levers that can be actuated by the driver are replaced by corresponding electrical or hydraulic servo-controls. When using a servo-controlled manual gear change, the driver merely has to send a command to a control unit to change to a higher or a lower gear and the control unit independently performs the gear change by acting on the control of the butterfly valve and on the various servo-controls.
For the correct management of the gear change operations, the control unit normally uses the transmissibility function of the clutch, i.e. the bi-univocal function that associates each position of the clutch (clutch position determined by a hydraulic or electric actuator controlled by the control unit) with a respective torque value transmitted by the clutch between the drive shaft and the primary shaft of the gear change.
The transmissibility function of a new clutch may be readily determined with a high degree of accuracy by simple experimental tests; however, the transmissibility function undergoes continuous change as a result of the wear of the clutch. If it is to be used, therefore, the transmissibility function of the clutch must be continuously updated during the use of the vehicle so as to take account of the changes continuously taking place in the clutch.
A number of methods have been proposed for updating the transmissibility function of a clutch during the normal use of the vehicle, in order to enable a continuous updating of the transmissibility function stored in a memory of the control unit of the vehicle. More particularly, the known methods of updating the transmissibility function of a clutch during the normal use of the vehicle, of the type disclosed in Italian Patent Application TO97A000086 filed on Feb. 4, 1997, entail the determination of this transmissibility function during a clutch actuation at the vehicle starting stage.
Using the known methods of the type described above, however, the correct determination of the transmissibility function is scarcely repeatable as it can be performed only when particular favourable conditions are present and, therefore, not during any vehicle starting stage. The fact that the determination of the transmissibility function is scarcely repeatable is a particular drawback as the updating has to take place less frequently and it is difficult to apply filtering operations to the results obtained to eliminate drifts due to noise. Moreover, the accuracy with which the transmissibility function is determined using the known methods described above is relatively low and not always able to satisfy the requirements of the control logics used in modern servo-controlled manual gear changes.
The object of the present invention is to provide a method of updating the transmissibility function of a clutch during a gear change, which is free from the drawbacks described above and which can, in particular, be readily and economically embodied.
The present invention therefore relates to a method of updating the transmissibility function of a clutch during a gear change as set out in claim 1.